Purpose of Strange pcb track

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Mar 9, 2015.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
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    I have attached some of PCB's showing strange PCb track. (zoom out file to 50% for clarity).

    What is their purpose. Shouldn't they be straight way connected?
     
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  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The wiggled lines can be seen as delay lines.
    This is done to have signals to arrive at the same time at the end of the line.

    Bertus
     
  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Indeed -- Or, perhaps, printed inductors...

    Best regards
    HP
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Since someone went to a lot of trouble to make all the wiggles I doubt they should "be straight way connected".

    Inductance is one possibility, equal delay another, so is some small but defined resistance.

    What is this thing where you found this board?
     
  5. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Those lines look eeriely similar to heating pads... perhaps they're there to keep the PCB at a constant temperature because it's a very sensitive type of circuit?
     
  6. Roderick Young

    Member

    Feb 22, 2015
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    I can't know the reason in this particular circuit, but when we did things like that on computer motherboards, it was in order to have (electronically) equal trace lengths. It might make a difference if it is clock distribution, or parallel data.
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    they look like printed inductors, quite a bit of consuumer electronics had to put them on to reduce em radiation. the govt put on limits for interference.
     
  8. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    One last possibility is high accuracy analog to digital conversion
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It would help to know the boards application?
    Max.
     
  10. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
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    It is very fast DIO board (upto 50Mhz).
    I have noticed that tracks which had small distance between them, only those where made wiggled.
    Tracks which had large distance very straight lines.

    So I think correct reason would be
    This is done to have signals to arrive at the same time at the end of the line.
     
  11. alfacliff

    Well-Known Member

    Dec 13, 2013
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    if the wiggles were to make the signals arrive at the same time, they would probably be different lengths to compensate for the rest of the board or circuitry.
     
  12. BReeves

    Member

    Nov 24, 2012
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    Except for the two at the left, they are different lengths,
     
  13. alfacliff

    Well-Known Member

    Dec 13, 2013
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    those wiggles dont look very long, it takes about 11 inches to make a nano second of delay, unless that is an extremely high frequency board (not normally phenolic pcb) the delay difference would be neglagable.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Found in the Wiki description on Delay Lines.

    "In modern computers operating at gigahertz speeds, millimeter differences in the length of conductors in a parallel data bus can cause data-bit skew, which can lead to data corruption or reduced processing performance. This is remedied by making all conductor paths of similar length, delaying the arrival time for what would otherwise be shorter travel distances by using zig-zagging traces."
    Max.
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
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    The technical term is: "data race".
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    Printed inductors are mainly spirals - on some of the pld floppy disk drives the spindle motor was pretty much built on a circular PCB, the coils were flat air-cored units glued to the PCB, these were surrounded around all of them by a zig-zag track - that was the PG winding.
     
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  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    and most of those printed circuit boards are fiberglass not phenolic. phenolic isnt stable enough and the impedance changes with humidity. plus the length of the traces isnt enough to make much difference at the frequencies that phenolic will work at. even the curves in the traces have to be proper, a right angle like those will cause an impedance bump with reflections. have to read up on stripline or microstrip for more info if you want it.
     
  18. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    is there a temperature sensitive component above that section of the board? Heat sensor, crystal, ... ? I agree that it could be for a heating element.

    There are bed heaters for RepRap 3D printers using a similar design on PCBs - no though-hole components on-board though.
     
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